I guess that in this case, if I was involoved, I would take that person aside (after class) and tell them that the class, in the majority, feels afraid to practice with him since many accidents take place then. I don't know if he is the type that would listen or not, but in both cases, this would be my first step. Maybe he is not aware of this (and believe me, people can hurt you so many times in training and not feel they do it). If this doesn't work, talk with your sensei, maybe he as the teacher should talk with the guy.

Now in basic- if he is not doing it on perpose, maybe he's working in his own style (you did say he is from another dojo), then he should work slower and take more care. No aikidoka can come and do as they please, it is the job of both training partners to keep safe while working together.

If he doesn't care about what is happening, then his place is not in the dojo, and the group has a right to say so if their health is in danger, because the next time might be a life threatening situation.

In our dojo, we put alot into training, and for some we might be called- training hard. But we have bounderies, we take care. When I train with people from other dojos (in seminars etc), I train softer, since I don't know who they are, what rank they are and so on, if I feel I can work faster, harder or so with them, I will, but I let my feelings direct me or I ask them.

I'm not saying there can't be accidents in aikido, of course there can, but not in the situation you discribe.